1. Field of Invention
This invention relates to a hinge to be used for a door such as an ordinary swing door that turns around a set of hinges, a flap door including a vertically pivoting flap door typically used for a toilet lid or the like.
2. Prior Art
There have been known hinges for doors of the type that utilizes a viscous fluid such as polyisobutylene or a similar high molecular viscous fluid substance in combination with a spring in order to obtain a high resistivity against any flinging motion of the doors in the direction through the use of the viscous shearing resistance of the former and the torsional resistance of the latter and induce a smooth and easy rotary movement for opening in the other direction through the effect of the spring.
However, with a door hinge of the type as described above where the resilient force of the spring of the hinge is used to bias the door only in the direction of opening the door around a rotary shaft, it can become very heavy when it is being closed since the hinge of a flap door is so designed that the spring force is utilized to facilitate the opening motion of the door, which is then locked at its open position. In order to make a door provided with such a hinge to be closed without difficulty, the hinge may require an additional mechanism which in turn makes the overall hinge structure a very complicated one.
It is therefore an object of the present invention to provide a door hinge which is free from the above described disadvantage of a conventional one. More specifically, a first object of the invention is to provide a door hinge comprising a spring that plays the role of both a torsion spring and a compression spring, wherein its resilient force is used for axially pressing a movable cam against a matching fixed cam it comprises and thereby facilitating the opening and closing motion of the door with which it is used by giving said cams such specific configurations that the spring accelerates the opening motion of the door from a given angular position of the door and locks the door at a particular open position and at a closed position.
A second object of the invention is to provide a door hinge which is, in addition to the features as described above with reference to the first object of the invention, provided with a damping capability and a function of generating a torque to accelerate the opening motion of the door with which it is used from a particular angular position of the door over a relatively wide range and holding the door open to a particular angular position.
A third object of the invention is to provide a door hinge which is provided with not only a damping capability but a function of generating a torque to accelerate the opening motion of the door with which it is used in the initial stages of the opening motion up to a given angle and that of generating a resistance against closure of the door which is increased as the door approaches the closed position so that the door may be closed smoothly and softly.